The most important objectives of wireless communications, broadcasting, telemetry, infrared and in general “radio” systems as well as “wired” systems include: power and bandwidth or spectrum efficiency combined with robust Bit Error Rate (BER) performance in a noisy and/or strong interference environment. These system objectives are specified in numerous systems including wireless communications and cellular systems, satellite systems, mobile and telemetry systems, broadcasting systems, cable, fiber optics and practically all communication transmission systems. A partial list of publications, references, and patents are provided separately below. The cited publications, references [1-23] and patents [P1-P8], and the references within the aforementioned publications contain definitions and descriptions of many terms used in this new patent disclosure and for this reason these conventional terms and definitions will be described only briefly, and highlighted on a case by case basis.
Robust or high performance Bit Error Rate (BER) specifications and/or objectives are frequently expressed in terms of the required BER as a function of Energy per Bit (Eb) divided by Noise Density or simply noise (No), that is, by the BER=f(Eb/No) expression. Low cost, reduced size, and compatibility and/or interoperability with other conventional or previously standardized systems, also known as “legacy systems,” are highly desired. Several standardization organizations have adopted modulation techniques such as conventional Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Offset Quadrature Phase Shift Keying (OQPSK) also designated as Staggered Quadrature Phase Shift Keying (SQPSK), and pi/4-QPSK (or π/4-QPSK) techniques including differential encoding variations of the same. See publications [1-23] and referenced patents [P1-P8] for examples and further description. For spectrally or spectrum efficient signaling (such as band-limited signaling), these conventional methods exhibit a large envelope fluctuation of the modulated signal, and thus have a large increase in peak radiated power relative to the average radiated power. For these reasons such systems are not suitable for BRA, robust BER performance NLA operated RF power efficient systems.
Within the present state of the technology, for numerous BRA Transceiver applications, it is not practical to introduce band-pass filtering after the NLA power efficient Radio Frequency (RF) final amplifier stage. Here we are using the term “Radio Frequency” (RF) in its broadest sense, implying that we are dealing with a modulated signal. The RF could be, for example, as high as the frequency of infrared or fiber optic transmitters; it could be in the GHz range, for example, between 1 GHz and 300 GHz or more, or it could be in the MHz range, for example, between about 1 MHz and 999 MHz, or just in the kHz range. The term RF could even apply to Quadrature Modulated (abbreviated “QM” or “QMOD”) Base-Band (BB) signals or to Intermediate Frequency (IF) signals.
In conventional BPSK, QPSK, OQPSK or SQPSK, and differentially-encoded phase-shift keying systems variants of these systems, such as DBPSK and DQPSK, as well as in pi/4-DQPSK and trellis coded QPSK and DQPSK, large envelope fluctuations require linearized (LIN) or highly linear transmitters including frequency up-converters and RF power amplifiers and may require expensive linear receivers having linear Automatic Gain Control (AGC) circuits. A transmitter NLA reduces the time domain envelope fluctuation of conventional QPSK type of band-limited signals and this reduction of the envelope fluctuation, being a signal distortion, is the cause of spectral restoration or spectral regrowth and the cause of unacceptably high levels of out-of-band spectral energy transmission, also known as out-of-band interference. Additionally, for conventional BPSK, QPSK, and also Quadrature Amplitude Modulation number (QAM) signals, undesired in-phase channel (I) to quadrature channel (Q) crosstalk is generated. This crosstalk degrades the BER=f(Eb/N0) performance of the modulated radio transmitter.
Experimental work, computer simulation, and theory documented in many recent publications indicates that for band-limited and standardized BPSK, QPSK, OQPSK or SQPSK or pi/4-QPSK, and QAM system specifications, very linear amplifiers are required to avoid the pitfalls of spectral restoration and of BER degradation. Linearized or linear amplifiers are less RF power efficient (during the power “on” state, power efficiency being defined as the transmit RF power divided by DC power), are considerably more expensive and/or having less transmit RF power capability, are larger in size, and are not as readily available as NLA amplifiers. The advantages of NLA over LIN amplifiers are even more dramatic at higher RF frequencies, such as frequencies above about 1 GHz for applications requiring low dc voltage, for example applications or systems operating on size “AA” batteries having only 1.5 Volt dc and for high RF modulated power requirements, for example transmit RF power in the 0.5 Watt to 100 Watt range.
Published references [P1 to P8] and [1 to 23] include additional background information. These references include descriptions of binary-state and multiple-state Transmitter/Receiver (Transceiver) or for short (“TR”) systems that are suitable for NLA. In the aforementioned references Processors, Modems, Transmitters, Receivers and Transceivers, suitable for NLA, have been described, defined and designated as first generation of Feher patented Quadrature Shift Keying (FQPSK). For example, in reference [22] published on May 15, 1999 the authors Drs. M. K. Simon and T. Y. Yan of JPL/NASA-Caltech present a detailed study of Unfiltered Feher-Patented Quadrature Phase Shift Keying (FQPSK). In references [1-22] and patents #[P1-P8] numerous first generation FQPSK technology based terms, and terms other than the FQPSK abbreviation/acronym have been used. In addition to FQPSK Transceivers, these first generation of systems have been also described and/or defined as: Feher's Minimum Shift Keying (FMSK), Feher's Frequency Shift Keying (FFSK), Feher's Gaussian Minimum Shift Keying (FGMSK), Feher's Quadrature Amplitude Modulation (FQAM) and/or Feher's (F) Modulation/Amplification (FMOD). Additionally terms such as Superposed Quadrature Amplitude Modulation (SQAM), Intersymbol Interference and Jitter Free (IJF) and/or IJF-OQPSK have been also described in Feher et al.'s prior patents and publications, each of which is incorporated by reference.
In the cited patents and other references, among the aforementioned abbreviations, acronyms, designation, terms and descriptions the “FQPSK” abbreviation/term has been most frequently used to describe in most generic terms one or more of these afore described Feher or Feher et al. first generation of Non-Linearly Amplified (NLA) inventions and technologies. The 1st generation of FQPSK systems have significantly increased spectral efficiency and enhanced end-to-end performance as compared to other NLA systems. RF power advantages, robust BER performance, and NLA narrow spectrum without the pitfalls of conventional BPSK and DBPSK, QPSK and OQPSK have been attained with these 1st generation FQPSK systems and methods. The generic 1st generation terms such as FQPSK, as well as other previously mentioned terms/acronyms are retained and used in this description to describe the new BRA, Code Selectable (CS), Modem Format Selectable (MFS) and modulation-demodulation Mis-Matched (MM) filtered architectures and embodiments of “2nd generation” FQPSK Transceivers.
While these earlier issued patents and publications describe material of a background nature, they do not disclose the original new enhanced performance bit rate agile and modulation agile/selectable technologies disclosed in this new invention.